#!/bin/bash
echo '>> before shift '
echo 'para count is ' $#
echo '$1 $2 $3 is ' $1, $2, $3.
shift 2
echo '>> after shift 2'
echo 'para count is ' $#
echo '$1 $2 $3 is ' $1, $2, $3.

aa="aaaaabcded";
echo ${aa:-bb}
echo ${bb:-bb}
echo ${bb:=aavalue}
echo ${bb:?"String is not define"}
echo ${aa:+"aa is exist"}
echo ${aa:1:2}

echo ${aa#ab}
echo ${aa##aa}
echo ${aa##ba}
